In recent years, in order to cope with rapid increases in image and video information in an information society, information recording and reproducing apparatuses are increasing in capacity and reducing in size. In information recording and reproducing apparatuses using light, because recording density depends on optical wavelengths, light having a short wavelength is used to aim at implementing high density. For a method of implementing recording density not depending on wavelengths, attention is focused on recording and reproduction principles using near field light. In information recording and reproducing apparatuses using magnetism, near field light assisted magnetic recording is regarded as a promising candidate for the next generation recording and reproduction principles, in which in order to isolate and magnetize a micro-area on the surface of the recording medium, near field light is applied only onto the micro-area for heating to reduce the coercivity, and then the micro-area is magnetized.
Heretofore, for recording information on a recording medium, a so-called longitudinal recording method is conducted, in which micro-areas in a recording layer are magnetized in the direction parallel with the surface of the recording medium. Because of the problem of thermal fluctuations, it becomes difficult to improve recording density. In order to solve this problem, a so-called perpendicular recording method is being adopted, in which micro-areas in a recording layer are magnetized in the direction perpendicular to the surface of the recording medium. In this method, because it is difficult that the north pole and the south pole make a loop in a recording layer, energy is more stable and resistant to thermal fluctuations than longitudinal recording method. In order to further improve recording density, such a recording medium having a stronger coercivity is being adopted as a recording medium for the purpose of suppressing the influence of the magnetic domains adjacent to each other and thermal fluctuations to the minimum. On this account, even in the perpendicular recording method described above, it becomes difficult to record information on the recording medium.
Then, attention is focused on a method in which to a recording medium having a strong coercivity, a micro-area is instantaneously heated to reduce the coercivity for magnetization and recording. This is a method in which an element to be a heat source is formed near a magnetic recording element mounted on an air bearing slider and the magnetization of the recording layer of a medium is reversed by a magnetic field generated by the magnetic recording element while heat emitted from the heat source is heating the surface of the recording medium. Because the coercivity of the recording layer is high, the area once magnetized can stably exist against thermal fluctuations even though the area is close to the adjacent area. This is called a heat assisted magnetic recording method. The important factors of high density recording in the heat assisted magnetic recording method are that the area heated for assistance is made smaller as much as possible and only the area desired to record is heated. In addition, it is also important to make the magnetic pole smaller by which a magnetic field is generated, and it is necessary to magnetize only a micro-area in the heated area as much as possible. As the method that can switch on and off at high frequencies and heat is applied only onto the area in the size of a few to a few tens nm, near field light can be utilized. This is called a near field light assisted magnetic recording method.
The head according to the near field light assisted magnetic recording method has a structure in which a near field light generating element is provided adjacent to a recording magnetic pole of an existent magnetic head. The near field light generating element is scatterer formed of a thin film metal, for example, in which light from a laser is applied to the scatterer to generate near field light in a micro-area (Patent Reference 1; JP-A-2004-158067).
In addition, such a structure is also proposed in which a metal thin film in a bow tie shape is formed on the under surface of a head, light is perpendicularly applied from above a recording medium to generate near field light, and the near field light is overlapped with the area onto which a magnetic field is strongly applied. In this near field light assisted magnetic recording head, a near field light generating element is a bow tie shaped metal of a flat film formed on the under surface of the head, in which light from a laser is led by an optical fiber, reflected in a mirror, and applied onto the bow tie, whereby near field light is generated in a gap in the center of the bow tie. Moreover, because this bow tie also serves as a magnetic recording element, the surface area of a medium heated by the near field light is matched with the area magnetized by a magnetic field. Thus, a micro-spot by the near field light can be made smaller to the limit, and this is suited for high density recording (Patent Reference 2; JP-A-2002-298302).
Patent Reference 1: JP-A-2004-158067
Patent Reference 2: JP-A-2002-298302